a. Field of the Invention
The present invention relates to an apparatus for regenerating wet spent active carbon by heating same at high temperatures.
b. Description of the Prior Art
With the recent strengthening of the controls on the discharge of various kinds of waste water, the use of the active carbon adsorption method, as an advanced treating method, is on the increase. At the same time, an apparatus for the regeneration of spent active carbon is also regarded as constituting an important factor of waste water treating measures. The spent active carbon to be subjected to regeneration is usually submerged, that is, held in the state of being mixed with water so as to be convenient for handling at the time of storing, transport, etc. Accordingly, when it is supplied to a regeneration apparatus, it is ordinarily supplied as wet spent active carbon after separating most of the water beforehand by means of a mechanical solid-liquid separation device.
As the means for the regeneration of wet spent active carbon, there have hitherto been adopted an apparatus which is devised so that the spent active carbon-to-be-treated is allowed to descend within a regeneration tube made of a heat resisting metal which is installed inside a heating furnace while heating it indirectly from the outside by means of a high-temperature combustion gas (which is obtained from the combustion of fuel) and supplying a regeneration gas such as steam or an appropriate reaction gas by way of the lower part of said tube so as to contact the spent active carbon, an apparatus which is devised so that spent active carbon-to-be-treated is introduced into a fluidized bed type furnace employing a high-temperature combustion gas as a fluidizing medium, thereby heating the spent active carbon directly with said combustion gas as well as bringing it in contact with said gas, or an apparatus which is devised so that the spent active carbon is first supplied to the uppermost hearth of a multi-hearth furnace (Herreschoff Furnace) and is scraped so as to fall onto the lower hearth in succession while supplying a high-temperature combustion gas from the lower part of said furnace, thereby heating the spent active carbon directly with the combustion gas as well as bringing it in contact with the same. All of these conventional regeneration apparatuses are supposed to perform the regeneration through three fundamental process steps of drying, calcination and reactivation. However, since the wet spent active carbon-to-be-treated usually contains a fair quantity of water, even after a dewatering treatment, the process of drying by evaporating said water in the conventional regeneration apparatuses entails a great thermal load, resulting in economical inferiority of these apparatuses. Hence, there has previously been proposed an apparatus which combines the foregoing indirect-heating type regeneration apparatus with an evaporation type drier utilizing a high-temperature exhaust gas arising from the apparatus as the source of heat for drying and installed outside the heating furnace (cf. U.S. Pat. No. 4,008,994). According to the proposed apparatus, as the spent active carbon can be almost dried through evaporation beforehand by virtue of the sensible heat of a high-temperature exhaust gas within the drier and thereafter calcined and reactivated within the regeneration tube, not only the quantity of fuel comsumption but also the quantity of expensive heat-resisting metallic material required can be reduced compared with the conventional indirect-heating type regeneration apparatuses. However, this apparatus is still defective in that there is a necessity for providing a special drying means in recovering the heat of said exhaust gas, entailing a great deal of cost of equipment.